10312 EVERGREEN WAY SONIC Geotech Report 2023-05-25

Geotechnical Engineering Report 7 January 8,2021 Glint Car Wash and Sonic Everett,Everett,Washington RGI Project No.2020-643-1 Soils may be proofrolled with a heavy compactor, loaded double-axle dump truck, or other heavy equipment under the observation of a RGI representative. This observer will assess the subgrade conditions prior to filling. Subgrade soils that become disturbed due to elevated moisture conditions should be overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI recommends that the earthwork portion of this project be completed during extended periods of warm and dry weather, if possible. If earthwork is completed during the wet season (typically November through May) it will be necessary to take extra precautionary measures to protect subgrade soils. Wet season earthwork will require additional mitigative measures beyond what would be expected during the drier summer and fall months. 5.2.4 STRUCTURAL FILL Once site preparation is complete, cuts and fills can be made to establish desired building grades. Prior to placing fill, RGI recommends proof-rolling as described above. RGI recommends fill below the foundation and floor slab, behind retaining walls, and below pavement and hardscape surfaces be placed in accordance with the following recommendations for structural fill. The suitability of excavated site soils and import soils for compacted structural fill use will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot be consistently compacted to a dense, non-yielding condition when the moisture content is more than 2 percent above or below optimum. Optimum moisture content is the moisture that results in the greatest compacted dry density with a specified compactive effort. The native soils are moisture sensitive and may require moisture condition prior to use as structural fill.The sandy native soil may be suitable for use as structural fill if the moisture can be properly controlled at the time of compaction if the construction occurs in dry weather. If the construction occurs in winter or extended to wet season, it may be necessary to import clean, granular soils to complete site work that meets the grading requirements listed in Table 2. Corporate Office 17522 Bothell Way Northeast Bothell,Washington 98011 Phone 425.415.0551• Fax 425.415.0311 1414/4'.riley-group.com